What is the "UpdaterStartupUtility" and why do I need it?

I don't get it when starting Safari. I get it when I start up the computer. Every time. And so far nothing has stopped it from showing up, even Mojave.

You can try —

To Change the Adobe Updater preferences, do the following:

1. Start the Adobe Updater application from /Applications/Utilities/Adobe Utilities/Adobe Updater5/.
2. When the update screen appears, click the Preferences link.
3. Uncheck the Automatically Check for updates checkbox and click OK.

Disable automatic check for updates in Adobe Creative Suite 3

Updater Startup Utility is from Adobe software. If you are using Adobe Flash Player it may be from a bogus installer you downloaded. To see where it is installed and delete it run Etrecheck.

Etrecheck  It is a diagnostic tool that will show a snapshot of your system. It should identify where the updater is installed. After it runs post the log file here. It will contain no personal information.

To post the log file copy & paste it using the Page icon in your reply window:

If you get that when starting Safari:

in the Safari menu open Preferences, open "Advanced", check "Show Develop menu in menu bar".

Shutdown Safari.

Open Safari while holding the Shift key, the "message" should not popup, then in the new Develop menu point choose "Empty Caches".